Where Do Scoring Chances Come From?

Ryan Pike
December 01 2014 11:30AM

It's Monday and we're all on a high after a really fun Grey Cup game last night, so it's probably good time to chat stats!

We've been tracking two key metrics here at FlamesNation: scoring chances and zone entries. The interesting thing is how they mesh together.

SCORING CHANCES

Scoring chances have been a staple stat here at FlamesNation for many years.

Short form: scoring chances are shot attempts - missed shots, blocked shots or shots on goal - taken from within the "home plate" area shown below.

Screen Shot 2014-11-30 at 12.27.54 PM

The logic behind valuing scoring chances is that the home plate area is the part of the ice where shooters tend to have the highest shooting percentage. In essence, shots here have more value. Teams can increase their odds of winning by keeping their opponents to the outside - out of the scoring chance area - because it minimizes their odds of scoring. (Fun fact: this is where the term "low percentage shot" comes from!)

Even-strength scoring chances are often used as a measure of how much a player contributes to the success of their team. Much like Corsi (Close) and Fenwick (Close), scoring chance percentage is held as a predictor of wins and standings points.

ZONE ENTRIES

One of the newer things being studied by the analytics community (stick-tap to Eric Tulsky for driving the study of them), zone entries are gradually increasing in their importance. Why? Well, it's all about possession.

Let's say you're a team with the puck, ready to attack. What do you do?

Well, you go to the net. But the other team is trying to stop you. So you have to get into the zone and get the puck into the scoring chance area. There's two ways you can do that.

  • You can dump the puck into the zone, giving up possession but potentially getting the puck behind the defenders. If you're fast, you can regain possession and gain position. If you're not fast, you lose possession and have to work to regain it.
  • You can carry the puck into the zone, retaining possession but having a potentially tougher time getting into the zone. After all, the puck is smaller and can move faster than a 200 pound hockey player.

The pros and cons of the two approaches have been juggled by both the coaching and analytics communities. There's no one right approach, but more and more the analytics community is pointing towards  gaining and retaining possession as incredibly important to goals and wins (and long-term success).

For the sake of analysis, this season we've been tracking zone entries at FlamesNation. I've interpreted things as follows: if you enter the zone in a controlled manner and don't immediately give up possession voluntarily, you get credited with a carry-in (e.g., you can't skate a foot over the blueline and chuck it into the corner). If you chuck the puck over the blueline into the zone and voluntarily give up possession, or do so pretty quickly after crossing the line, it's a dump-in. Any other method of entry into the zone (the other team ices it, the other team takes a penalty, the other team falls back into their own zone) are ignored. (You've probably seen the fun tables after each game with breakdowns to that effect.)

The interesting aspect, to me, and what we're looking at right now is at the intersection of zone entries and scoring chances.

SCORING CHANCES AFTER ENTRIES

There's a relatively simple question driving the first chunk of this inquiry: Where do scoring chances come from? In a more specific sense, we're looking at what kinds of entries are followed by scoring chances and how often.

Over the first 25 games of the 2014-15 season, the Calgary Flames have generated 359 even-strength scoring chances. (For the curious, that's about 14 chances per game.)

So when do these chances happen, relative to zone entries?

The Flames had 217 even-strength chances within 30 seconds of a carry-in entry, representing approximately 60.4% of all chances. On the flip-side, they had 105 chances within 30 seconds of a dump-in, representing approximately 29.2% of all chances. The remainder of the chances happened via other circumstances - primarily icings and opposition giveaways in the offensive zone.

ENTRIES THAT RESULT IN SCORING CHANCES

Okay, given that most of Calgary's chances happen after carry-ins, why don't they (a) carry the puck in like crazy people and/or (b) have a zillion scoring chances?

Well, most of their entries are dump-ins - 1,296 even-strength dump-ins versus 800 even-strength carries. This can be for a million different reasons - strategy (getting behind defenders with speed), situation (tired players buying time for a line change), injury (players trying to avoid contact) or lack of skill. However, even acknowledging this disparity in carries and dumps, something interesting emerges from the data.

Carry-ins, even with how rare they are relative to dump-ins, are much more effective at generating chances. Calgary converts carry-ins to scoring chances at a rate of about 27.1%, while dump-ins convert at about 8.1% - indicating that carrying in the puck is more than THREE TIMES more likely to result in a scoring chance than a dump-in.

It makes sense that that would be the case, given the fact that dump-ins (by definition) give up possession, but that carry-ins are that much more instrumental in scoring chances is itself quite noteworthy.

SUM IT UP

I'll be honest, I find the numbers pretty neat.

As we get further into the season, we'll be digging into the individual-level data - which is a bit more messy and prone to sample-size irregularities, which is why I'm delaying looking at them until around the half-way mark.

It's also interesting to see what happens later in the season. Can the Flames maintain their speed game? If you follow the team - and if you're one of our regular readers (thank you!), you probably do - you know that the guys that generally rush in with speed are folks like Sean Monahan, Johnny Gaudreau, Mikael Backlund, Paul Byron and Sven Baertschi.

If I know that and you know that, and we presume that the other 29 NHL teams have advance scouts, video coaches and at least a cursory knowledge of coaching and strategy, then the big question will be how long the Calgary Flames can play the speed game effectively with the other teams trying to counter it.

(For the record, this is what the talking heads are referring to when they say "The Flames aren't going to surprise anybody going forward.")

It's going to be fascinating, both in the data and on the ice, to see them try.

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Ryan Pike has covered the Calgary Flames since 2010. He's Senior Contributing Editor at FlamesNation, a Senior Writer covering the Flames and the NHL Draft for The Hockey Writers, and a correspondent for the Fischler Report. He's just trying to capture the spirit of the thing.
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#1 Bean-counting cowboy
December 01 2014, 11:54AM
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Great insight - very interesting indeed. This is why Johnny G is crucial to this team's possession and scoring chances - he carries the puck in!

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#2 Burnward
December 01 2014, 11:58AM
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This is what advanced stats should be!!!

Great stuff.

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#3 wot96
December 01 2014, 12:21PM
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Good article.

How long can the Flames continue their speed game? As long as the Flames' fast players are faster than the opposition's slow players, especially at home when they can put aforementioned speed players on against the other team's 5/6 defenders.

Plus, any thought that the Flames cannot adjust is misguided. The Flames adjusted just fine to NJ, which took away the stretch pass.

Speed with skill is still a lethal combination, even if the other side knows what's coming.

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#4 Jeff In Lethbridge
December 01 2014, 12:23PM
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seems like it didnt take many games this year before apposing teams started giving Gaudreau lots of attention. I think he draws attention away from others, giving them more opportunity. this i believe has really boosted Hudler's numbers.

looking forward to seeing what happens when colburne, stajan, raymond and backlund are back...

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#5 Jake the Snail
December 01 2014, 12:25PM
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"If I know that and you know that, and we presume that the other 29 NHL teams have advance scouts, video coaches and at least a cursory knowledge of coaching and strategy, then the big question will be how long the Calgary Flames can play the speed game effectively with the other teams trying to counter it."

- I think Hartley is a smart enough coach that he can figure out a way to counterattack the oppositions counter! He did win a Cup, after all...

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#6 Walter White
December 01 2014, 12:49PM
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Jeff In Lethbridge wrote:

seems like it didnt take many games this year before apposing teams started giving Gaudreau lots of attention. I think he draws attention away from others, giving them more opportunity. this i believe has really boosted Hudler's numbers.

looking forward to seeing what happens when colburne, stajan, raymond and backlund are back...

Are those clowns even good enough to play on this team now....?

WW

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#7 MWflames
December 01 2014, 12:56PM
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Must take a lot of effort to track which chances come from which zone entries. Kudos.

Also, carry-ins may be more efdective because we dump the puck in so much. If teams know that they may sit back more than if they though we were going to carry it in more often

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#8 wot96
December 01 2014, 01:12PM
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@Jake the Snail

That sounds like something KLowe would say.

Just say no.

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#9 playastation
December 01 2014, 01:14PM
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Walter White wrote:

Are those clowns even good enough to play on this team now....?

WW

Clowns?

Backlund can play center and shut down other centers. Granlund or Jooris can be moved to wing, making the team BETTER. Colborne can play wing, maybe take out one of the facepunchers, once again adding size and skill, once again, making the team better. Raymond adds goal scoring, lets remember, most of the offense comes from the defense. Adding skilled possession players is a good thing.

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#10 internuncial
December 01 2014, 01:29PM
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"Must take a lot of effort to track which chances come from which zone entries. Kudos.

Also, carry-ins may be more efdective because we dump the puck in so much. If teams know that they may sit back more than if they though we were going to carry it in more often

This. Exactly.

It's great to parse the numbers, but then there's the real world to deal with. I've always thought of dump/carry as kind of like run/pass (although I hate the football). Using both effectively keeps the other team honest. Or to look at it the other way: you get known for doing one all the time and defending against it becomes easier.

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#11 Avalain
December 01 2014, 02:13PM
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I was wondering about the zone entry counting. Do dump ins include the times when they dump the puck at the center line and go for a change? Because including those with the dump 'n chase kind of muddies the stats in terms of how effective dumping the puck can be offensively.

Edit: I'm sorry, I missed a whole paragraph up there when I read it the first time. I guess a better question would be "is it possible to count dump and chase separately from dump and change?"

Another number that could be interesting is how often they give up possession involuntarily when doing a carry in, since this is generally what the dump-in is trying to prevent. Personally, I hope to see the numbers still favour carry-in, simply because dump and chase games frustrate me.

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#12 Loxeus
December 01 2014, 02:41PM
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Explains why dumping and chasing never worked for any of Sutter's groups when he was here. I think around 100% of their zone entries were from dumps and nobody had the speed to actually do anything with them.

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#13 Erico
December 01 2014, 02:42PM
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@Avalain

I totally agree, dump and change is a very different thing than what it is being lumped in with...

I love the analysis, but I do think dump and change would skew the numbers in terms of what approach is more effective.

So I will just echo this question, what do the numbers say if dump and change are separated out?

I realize that is probably not realistic to gather those numbers, but maybe going forward?

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#14 Regularstatsguy
December 01 2014, 03:00PM
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This is the concern I have with CORSI and PDO.

They don't take into account the quality of scoring chances.

So take the Oilers for example. I'm sick of hearing them say our even-strength CORSI was excellent "so we played good enough to win". No you didn't. You floated 10 pucks from the boards at the blue line and gave up 5 scoring chances from the slot. More easy shots from the point with no traffic would not have increased your chance of winning because most goalie will catch them automatically - it has nothing to do with puck luck or sample size.

These kind of pronouncements only hurt the legitimacy of statistics because others point to them (rightfully) and say that the conclusion's drawn don't follow the numbers.

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#15 Robear
December 01 2014, 03:03PM
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@wot96

Loving the article Ryan and, as is my wont, I feel compelled to be greedy and ask for more!

In particular I recall hearing how some coaches have a hate-on for pucks lost at the opposing blue line, citing those as momentum killers and chance generators going the other way. Many a young player has been sat for "not getting the puck deep".

As important as it is to review how carrying the puck in increases a team's scoring chance stats would be to see what failed "carry-in" attempts does going the other way for the other team. After all, the point of the game is to score MORE than the other team, not just generate scoring chances.

I think this is one of those items that gets easily fed by the eye test when watching a game.

I also expect that we find that the reason many players dump in the puck is because its tough to do and many just dont have the skill to do it well!

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#16 sa
December 01 2014, 03:29PM
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Erico wrote:

I totally agree, dump and change is a very different thing than what it is being lumped in with...

I love the analysis, but I do think dump and change would skew the numbers in terms of what approach is more effective.

So I will just echo this question, what do the numbers say if dump and change are separated out?

I realize that is probably not realistic to gather those numbers, but maybe going forward?

As all teams dump and change, the stats would be skewed in a relatively equal manner across the league, wouldn't it?

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#17 beloch
December 01 2014, 03:54PM
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Most NHL teams track scoring chances and treat the data at special secret sauce. I'd love to see fans come together, standardize on a single scoring chance definition, and put scoring chance data for all games into a single data base. That'd be a goldmine! For example, we could start to answer questions like, "How good are Corsi, Fenwick, shots, etc. at predicting scoring chances, and how they compare to scoring chances when predicting goals?"

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#18 Avalain
December 01 2014, 04:00PM
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sa wrote:

As all teams dump and change, the stats would be skewed in a relatively equal manner across the league, wouldn't it?

Well, no, I don't believe so. First of all, teams tend to dump and change more often if they are being hemmed into their own zone. Perhaps the stat by itself wouldn't say very much, but it would be interesting to see the ratio of dump and change entries compared to zone entries where the team is at least attempting to retain possession (or at least keep pressure up).

That being said, the point is that if you include dump and change zone entries with dump and chase zone entries then you skew the percentage of scoring chances compared to when you carry the puck in.

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#19 Avalain
December 01 2014, 04:00PM
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sa wrote:

As all teams dump and change, the stats would be skewed in a relatively equal manner across the league, wouldn't it?

Well, no, I don't believe so. First of all, teams tend to dump and change more often if they are being hemmed into their own zone. Perhaps the stat by itself wouldn't say very much, but it would be interesting to see the ratio of dump and change entries compared to zone entries where the team is at least attempting to retain possession (or at least keep pressure up).

That being said, the point is that if you include dump and change zone entries with dump and chase zone entries then you skew the percentage of scoring chances compared to when you carry the puck in.

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#20 Tach
December 01 2014, 05:32PM
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Interesting and I always appreciate the good work on this site on stuff like this, but whenever I read about the zone entry correlation to goals/scoring chances/shot my reaction is "Of course they do."

If you think about it, many of the opportunities for carrying the puck in will be generated off of odd-man rushes (breakaway, 2 v 1, 3 v 2) and these are also the situations where scoring chances are more likely to be generated. The opposite is true of dump ins (more likely to dump it in 1 v 3 and it would also have been highly unlikely to generate a scoring chance). As a result, it is still very difficult to generate prescriptive tactical advice from these statistics. For example, forcing a carry across the blue line 1 v 3 might lead to counter attacks which lead to scoring chances against. This data doesn't address that at all.

There was a study a few years ago (and damned if I can find it now) using data from college hockey (Harvard I think) that tended to show that you were better off to re-group rather than to dump-in. I found convincing.

If we really wanted to draw prescriptive advice the types of data we would want would include where the other players were on the ice when a particular type of zone entry was attempted (was it 2 v 2, 3 v 3) and what the scoring chance results were, as well as the number of times the other team obtained a successful zone entry or scoring chance within 30 seconds of failed attempts as well.

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#21 Tach
December 01 2014, 05:35PM
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@beloch

I'm pretty sure Gabe Desjardins or someone already tested this and the correlation between scoring chances and shot attempt ratios was so high (.85 or .9 or something) that tracking scoring chances added very little predictive value over and above shot attempt figures.

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#22 savardianspinorama
December 01 2014, 06:40PM
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I love when writers end a sentence with a preposition.

"Where Do Scoring Chances Come From?"

Why not, "Where are Scoring Chances Generated?"

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#23 savardianspinorama
December 01 2014, 06:42PM
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savardianspinorama wrote:

I love when writers end a sentence with a preposition.

"Where Do Scoring Chances Come From?"

Why not, "Where are Scoring Chances Generated?"

What did I write that FOR?

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#24 Scalabis
December 01 2014, 06:49PM
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Sweeeeet article, Ryan!

Keep this work of making numbers more interesting and related to reality!

(OK, and fun too!)

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#25 BurningSensation
December 01 2014, 07:13PM
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"If I know that and you know that, and we presume that the other 29 NHL teams have advance scouts, video coaches and at least a cursory knowledge of coaching and strategy, then the big question will be how long the Calgary Flames can play the speed game effectively with the other teams trying to counter it."

That depends on what these counter strategies are...and other than 'back off so he doesn't turnstyle you wide' I don't know what they are.

What should we look for?

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#26 Canrock 78
December 01 2014, 08:15PM
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http://www.calgarypuck.com/2014/12/the-calgary-ava-leafs/

This is a good article worth the read.

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#27 beloch
December 01 2014, 08:41PM
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Canrock 78 wrote:

http://www.calgarypuck.com/2014/12/the-calgary-ava-leafs/

This is a good article worth the read.

TLDR version: Flames sv% is average. It's the sh% that's got their PDO pumped to #3 in the league. The Saturday Flames vs Coyotes game is an example of a game advanced stats say the Flames should have lost.

Quick retort: This article ignores context. The Flames led in fancy stats for about half the game, and then the Coyotes stormed back on the virtue of 35 minutes of chase effect. Likewise, the team has indeed been lucky with sh% so far this season, but the article ignores the context: The Flames have played most of the season without two of their best possession forwards. It also ignores visible progress in the rookies. i.e. You can track visible progress in the advanced stats of players like Gaudreau and Monahan. The Flames sh% will likely regress, but the team's CF% is likely going to progress, especially once Stajan and Backlund return.

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#28 SaskFlames
December 01 2014, 09:14PM
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I suppose I could be wrong, but I get the feeling Beloch that you did not read the whole article and CalgaryPuck.

While the article does not mention ScoreEffects, it also does not argue that Calgary is benefiting from good luck and nothing else.

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#29 beloch
December 01 2014, 10:28PM
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@SaskFlames

I admit I zoned out and skipped the concluding paragraph. Going back, I see the author ignored the evidence he presented and, instead, concluded that perhaps the Flames are indeed somehow defying advanced stats (e.g. by passing lots and making their shots count).

I confess I've had the same thought myself, but I also have to recognize it as an extraordinary claim that requires extraordinary evidence. If we had league-wide scoring chance data over several years we could indeed explore to what extent some teams can consistently defy advanced stats by playing, for example, a "pass first" style. Without that data, we're stuck in the same place Leafs fans were last year. We love our team and would love to think that they're defying advanced stats. Games like the one against San Jose happen, in which the Flames had an abysmal CF% of 38.0% but somehow outchanced their opponent 16 to 11. However, we don't even have access to scoring chance data for every game the Flames have played this season (some games are missing). We can't look at one, potentially grossly aberrant, game and conclude a trend exists.

My position is that we have to acknowledge that what we do know strongly suggests the Flames have been very lucky to have the record they've had so far (luck primarily in the form of sh%). However, the evidence doesn't support impending "doom by regression". Injuries and rookie progression suggest this team could have far better underlying numbers by the end of the season.

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#30 savardianspinorama
December 01 2014, 10:47PM
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beloch wrote:

I admit I zoned out and skipped the concluding paragraph. Going back, I see the author ignored the evidence he presented and, instead, concluded that perhaps the Flames are indeed somehow defying advanced stats (e.g. by passing lots and making their shots count).

I confess I've had the same thought myself, but I also have to recognize it as an extraordinary claim that requires extraordinary evidence. If we had league-wide scoring chance data over several years we could indeed explore to what extent some teams can consistently defy advanced stats by playing, for example, a "pass first" style. Without that data, we're stuck in the same place Leafs fans were last year. We love our team and would love to think that they're defying advanced stats. Games like the one against San Jose happen, in which the Flames had an abysmal CF% of 38.0% but somehow outchanced their opponent 16 to 11. However, we don't even have access to scoring chance data for every game the Flames have played this season (some games are missing). We can't look at one, potentially grossly aberrant, game and conclude a trend exists.

My position is that we have to acknowledge that what we do know strongly suggests the Flames have been very lucky to have the record they've had so far (luck primarily in the form of sh%). However, the evidence doesn't support impending "doom by regression". Injuries and rookie progression suggest this team could have far better underlying numbers by the end of the season.

A pox on you, dear sir, for even daring to compare our beloved Flames to the Leafs!

Luck is measured in many different ways, and while I agree the Flames have been somewhat lucky, this doesn't come even close to what took place with the Leafs or Avs last season.

And while it would be silly of me to predict a playoff spot for the Flames, and I won't, the difference between the Leafs, Avs and Flames is this: The Avs and Leafs had rosters whose players were already made up. The Flames are evolving.

There is much left to do.

But I wouldn't trade the Flames' roster or prospects for either the Avs or Leafs.

Would you?

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#31 Erico
December 02 2014, 09:14AM
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sa wrote:

As all teams dump and change, the stats would be skewed in a relatively equal manner across the league, wouldn't it?

Yes over a small sample size. But, I think if you looked at it over a half a season or longer you will see trends of success and failure. Teams dump and change more often if they are being dominated in their own end. I think over the long term you would see a statistical separation between the "oilers" of the league, and the good teams... haha

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#32 Jeff In Lethbridge
December 02 2014, 10:32AM
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savardianspinorama wrote:

I love when writers end a sentence with a preposition.

"Where Do Scoring Chances Come From?"

Why not, "Where are Scoring Chances Generated?"

"I love when writers end a sentence with a preposition."

your sentence also ends with a preposition :-D

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#33 The Last Big Bear
December 02 2014, 11:26PM
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"Where do scoring chances come from?"

They come from Johnny Gaudreau.

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#34 Jeff In Lethbridge
December 03 2014, 09:30AM
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The Last Big Bear wrote:

"Where do scoring chances come from?"

They come from Johnny Gaudreau.

isn't that the truth. Best advice to those playing on Gaudreau's line is, "go to the net, keep your stick on the ice, because the pass IS coming"

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#35 TrentonL
December 05 2014, 08:48AM
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Do you track dump and changes? i.e. how much does dump and chase efficiency improve if you cut out dump-ins where it wasn't even an attempt to generate offence?

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